Save PDFs of online sites, too, as you wouldn't want to need to look back at something and not be able to get online or find that the article has been removed since you read it.
Once you have a working thesis, write it down. After all, the generator can only create a thesis statement based on the information you provide.
And by writing down your thesis you will be forced to think of it clearly, logically, and concisely. And what about the fall of Hitler?
Readers are used to finding theses there, so they automatically pay more attention when they read the last sentence of your introduction. It should tell what you plan to argue, and it should "telegraph" how you plan to argue—that is, what particular support for your claim is going where in your essay.
Read through all instructions, and have a conversation with your instructor at the start of the project to determine his or her preferences and requirements.